Generally, a drum type washing method is a method of washing laundry using frictional force, generated between a drum rotated by a driving force transmitted from a motor and the laundry when detergent, washing water, and laundry are put into a drum of a clothes washing machine. In the drum type washing method, the laundry is minimally damaged and entangled and an effect of beating and rubbing the laundry can be achieved.
Moreover, according to a drive type, a conventional clothes washing machine is grouped into an indirect-coupled type clothes washing machine in which a driving force of a motor is indirectly transmitted to a drum through a belt wound around a motor pulley and a drum pulley, and a direct-coupled type clothes washing machine in which a rotor of a brushless direct current (BLDC) motor is directly coupled with a drum such that a driving force of the BLDC motor is directly transmitted to the drum.
Here, in the clothes washing machine in which the driving force of a motor is not directly transmitted to the drum but is indirectly transmitted to the drum through the belt wound around the motor pulley and the drum pulley, energy loss is generated during the transmission of the driving force and significant noise is generated during the transmission of the driving force.
Thus, in order to solve the problem of the conventional clothes washing machine, it is recent trend of widely using a direct-coupled drum type clothes washing machine using the BLDC motor.
With reference to FIG. 1, a conventional direct-coupled drum type clothes washing machine will be described in brief as follows.
FIG. 1 is an elevational sectional view illustrating a structure of the conventional drum type clothes washing machine including a tub 2 installed in a cabinet 1 and a drum 3 installed to rotate in the central region of the tub 2.
A motor is installed in the tear side of the tub 2. A stator 6 of the motor is fixed to a rear wall of the tub 2 and a rotor 5 is installed to surround the stator 6 and penetrates the tub 2 to be coupled with a shaft 4 of the drum 3.
Meanwhile, a door 21 is installed at the front side of the cabinet 1 and a gasket 22 is installed between the door 21 and the tub 2.
Moreover, between the upper inner side of the cabinet 1 and the outer circumferential upper side of the tub 2, a hanging spring 23 is installed to support the tub 2. Between the lower inner side of the cabinet 1 and the lower side of the outer circumference of the tub 2, a friction damper 24 is installed to damp vibration of the tub 2 generated during the dehydration.
Meanwhile, FIG. 2 is a perspective view illustrating an external appearance of the stator depicted in FIG. 1, and FIG. 3 is a perspective view illustrating a sectional core employed in the stator depicted in FIG. 2. A conventional stator core is manufactured by the following process. A metal sheet is pressed to make unit cores respectively having teeth 151, a base 150, and protrusion 500 for forming a coupling hole 500a at the opposite side of the teeth 151, the unit cores are stacked to form a core assembly, the core assembly is connected to each other in the circumferential direction so that the stator core, called as a “sectional core”, is completed.
The protrusion provides the coupling hole 500a required when the stator 6 is coupled with the rear wall of the tub and resists the fastening force of a bolt.
However, the manufacturing process of the stator 6 using the sectional core is complicated and there are a lot of material losses.
Thus, in order to reduce the material loss and to simplify the manufacturing process, a helical core, in which metal sheets having the teeth 151 and the base 150 are rotated and stacked in helical direction, is useful. However, since blanked metal sheet must be helically bent during the manufacturing of the helical core (HC), the protrusion for coupling the stator with the tub cannot be formed in the core.
This is because, in a case of forming the protrusion 500 in the inner side of the core when manufacturing the helical core, the width of the core where the protrusion is present is too large so that the core cannot be bent.
Thus, there is a demand for new structure of the stator capable of employing the helical core by which the core itself does not perform the same function as the protrusion of the section core but other part performs the function.
For reference, the important reason of guaranteeing sufficient strength of the protrusion having the coupling hole for coupling the stator with the tub is as follows.
In the drum type clothes washing machine for directly rotating the drum using the BLDC motor, a stator is directly installed to a fixing part of the rear side of the tub. However, in a motor of a high volume drum type clothes washing machine having weight of the stator equal to or greater than 1.5 Kg and the dehydration speed of 600 RPM to 2,000 RPM, due to the weight of the stator, vibration during the rotation at high speed, and trembling and deformation of the rotor 5, the coupling part of the stator 6 is damaged.
Particularly, in a drum type clothes washing machine using the BLDC motor of which stator 6 is coupled with the rear wall of the tub 2, since the radial direction of the stator 6 is approximately parallel to the ground, due to vibration generated during the operation of the drum type clothes washing machine, the connection part of the stator 6 with the rear wall of the tub 2 is more seriously damaged.
Thus, it is very important to guarantee sufficient strength of the protrusion having the coupling hole for coupling the stator 6 with the tub.